The present invention relates to an image forming apparatus used in an image forming method using a technique of electrophotography or electrostatic recording and a developing agent used to visualize an electrostatic charge latent image in this image forming apparatus.
In a method of electrophotography, a photoconductive substance is generally used to form an electrical latent image on a photosensitive member by various methods. The latent image is then developed with toner and, the toner image is transferred onto a transfer medium such as paper. Thereafter, the toner image is fixed on the transfer medium by various methods to obtain a copy.
Generally, toner is classified into dry and wet toners. Since wet toner has problems relating to evaporation, recovery, and smell of solvents, dry toner s prevalent in recent years.
Dry toner is a powder, and it is necessary to impart a number of functions to the toner particles in order to accurately form toner images. A dry electrophotographic developing agent is required to simultaneously have various characteristics, i.e., (1) to prevent offset during fixing and (2) to prevent smear by which, when a toner-fixed sheet is conveyed as n original in an ADF, the fixed toner peels off from the sheet, and the like.
To meet these demands, Jpn. Pat. Appln. KOKAI Publication No. 4-358159 has disclosed a method by which two kinds of waxes having different softening temperatures are contained in toner.
When two types of waxes are used, however, it is difficult to disperse these waxes uniformly in a single resin. Low dispersibility of waxes results in problems that masses of waxes stick to a photosensitive member to produce black dots in an image, electrostatic charging fails to scatter toner, and the backside of a copy sheet is contaminated by detached developing agent.